An Unexpected, Rare and Potentially Dangerous Bump in the Road: Appendiceal Mucocele

Abstract

Appendiceal mucocele is a rare pathologic entity with an incidence of 0.2% to 0.7% of all appendectomies.It is characterized by a distended appendix filled with mucoid material. These lesions are typically noted as incidental findings following radiographic or endoscopic evaluation. Patients are often asymptomatic or have nonspecific symptoms such as intermittent colicky abdominal pain. A 37-year-old man with no significant medical history presented with diarrhea and intermittent hematochezia for 4 months and associated mild lower abdominal cramping. Review of systems was negative for fevers, melena, weight loss, change in appetite, nausea, vomiting or early satiety. Physical exam revealed mild left lower quadrant discomfort with palpation. Laboratory studies were unremarkable. Stool studies including clostridium toxin and stool culture were negative. Subsequent colonoscopy showed erythematous mucosa in the rectum and recto-sigmoid colon as well as a submucosal lesion measuring 4 centimeters in the cecum (Fig 1). Biopsy revealed colonic mucosa with no pathologic abnormality. CT of the abdomen and pelvis with contrast showed a 10.6x3.0x3.2 cm tubular shaped mass that was appendiceal in origin, likely a mucocele with extension and intussusception into the ascending colon (Fig 2). The patient was treated with oral mesalamine and hydrocortisone enemas, which improved his symptoms. He was discharged home and had an outpatient uncomplicated laparoscopic appendectomy performed (Fig 3). Histology revealed a benign mucinous cystadenoma. Prompt resection of appendiceal mucocele is essential due to poor sensitivity of imaging studies to exclude a neoplastic component within the mucocele. Surgical approach is based on radiographic and endoscopic characterization. Laparoscopic or open appendectomy or hemicolectomy can be performed, with the more invasive approaches reserved for non-homogenous mucoceles with involvement of adjacent structures. Extreme care must be taken during resection to prevent seeding of the peritoneum with mucinous cells as this may lead to pseudomyxoma peritonei. Follow-up imaging in one year may be considered if the peritoneum was contaminated. Colonoscopy is essential in the pre-operative evaluation as approximately 20% of patients may have a concomitant colorectal adenocarcinoma. The course and prognosis depends on the histologic subtypes. Overall, survival is excellent (91-100%) following prompt resection of non-neoplastic appendiceal mucoceles.Figure: Colonoscopic image showing a 4 cm submucosal mass at the cecum.Figure: (A-Transverse cross-section, B-Coronal cross-section): Contrast-enhanced computed tomography scan showing a 10.6 x 3.0 x 3.2 cm tubular shaped mass (arrow) which measures just above fluid attenuation (26 Hounsfield units) and is believed to be appendiceal in origin, likely a mucocele. Also extension, intussusception into the ascending colon is noted.Figure: A- Intraoperative view of appendiceal mass during laparoscopic appendectomy. B- Excised specimen measuring approximately 10 am in largest diameter. C- Specimen transected to reveal gelatinous material.